RE: Flamethrower???
two things diff in that photo....it's a bow gun mount, which means short range and more volume, and it's a demo in which a non combat mix is used to create a more spectacular flame and smoke with less spectator hazard. ....as posted= Holllywood style.
Both of my flame tanks worked on a water stream with a bit of orange food coloring. Possible a LED would look OK, but doubt if it would carry the 4-6 feet of the stream, unless the area was pretty dark. Be interesting to see.